The present invention relates to a mobile radiotelephone formed by circuits enabling its user to receive incoming calls and set up outgoing calls, which device comprises:
an interface between the user and the circuits of the device, including a blocking/unblocking means for putting the interface in a blocking state to prevent the normal use of the radiotelephone when the interface receives a block-activation signal and for putting the interface in a service state to make the radiotelephone accessible to the user when the interface receives an unblocking signal.
The invention also relates to a method for protecting such a device.
Such devices are well known and find many applications, in the field of portable telephones. These devices are intended to accompany their users and it happens that these users leave them unnoticed for an instant at a frequented location. This may thus lead to the device being stolen or even used by a person who seizes the opportunity to exchange costly communications.
It is known from United States patent nr. U.S. Pat. No. 4,908,848 to block or restrict the use of said device.
However, this type of blocking is poorly adapted to radiotelephones, because one must not forget to block the device the moment one has finished using it and it is necessary for the user to put the radiotelephone in a blocking state by pressing some key on the keyboard.
It is an object of the present invention to provide a device of the type defined in the opening paragraph, well adapted to the use of mobile radiotelephones, which enables to resolve this problem of forgetting.
Therefore, such a device is characterized in that it comprises a timing circuit for supplying an activation signal to said blocking circuit after a predetermined period of inactivity of the device.
The idea of the invention is to avoid calls being made which are not authorized by the proprietor of the device. Furthermore, it is desired that incoming calls be processed in a transparent manner.
A characteristic feature according to which an access to said circuits for an outgoing emergency call is given provides the advantage that the device ensures a security function for anyone for whom, in the case of need, it is necessary to make this emergency call.